I recently had my iPAQ 2215 stolen. I may replace it with another (refurb) 2215, but I'm wondering - do all HP PDA's use the same version of MS Active Synch? What about other brands? In other words, what are my limitations regarding synching a new PDA to the calendar and contact (etc) data that's already on my desktop?

All Pocket PCs use ActiveSync which like the Windows Mobile OS, is made by Microsoft. So you won't need to do anything to use the replacement 2215. As long as you're using 3.1 you can sync to any Pocket PC, in fact. If you ever wish to download the latest version, you can do so for free from MS' site: www.pocketpc.com .